Manholes are commonly closed by manhole cover assemblies which are placed directly onto the top of the manhole and then embedded in concrete or asphalt. The weight of the manhole assembly is used to hold the manhole cover in position on top of the manhole. No seal is provided other than the weight of the manhole assembly. Over a period of time erosion of the asphalt or concrete will allow water to infiltrate into the manhole through the space between the cover and the top of the manhole. Excessive amounts of water infiltrating the manhole produces an increased burden on the sewer system.